• Brad Segebarth, Mark F Kurd, Priscilla H Haug, and Rick Davis.
• *OrthoCarolina Spine Center †OrthoCarolina Research Institute, Charlotte, NC ‡Health Partners, St Paul MN.
• J Spinal Disord Tech. 2015 Dec 1; 28 (10): 394-7.

Study DesignA retrospective cohort.BackgroundDegenerative spondylolisthesis (DS) with lumbar stenosis is a well-studied pathology and diagnosis is most commonly determined by a combination of magnetic resonance imaging (MRI) and standing radiographs. However, routine upright imaging is not universally accepted as standard in all practices. To the best of our knowledge, there has been no study investigating the incidence of missed diagnosis of DS evident only on standing lateral or dynamic radiographs when compared with sagittal alignment on MRI.ObjectiveThe authors hypothesize that supine MRI evaluation alone in lumbar degenerative disease will significantly underestimate the incidence of DS. Secondary hypothesis is that there will be no significant difference in detecting spondylolisthesis when comparing dynamic flexion-extension radiographs to standing lateral radiographs.MethodsWe retrospectively evaluated all patients presenting to spine clinic for degenerative lumbar conditions from July 2004 to July 2006 who had an MRI, upright lateral, and flexion-extension radiographs at our institution. The incidence of DS found on dynamic flexion-extension radiographs but not on MRI was determined. We then reviewed each and compared flexion-extension versus standing lateral views to determine whether there was any significant difference in detecting anterolisthesis.ResultsOf 416 patients with eligible studies, 109 were found to have DS at levels L4-L5, L5-S1, or L3-L4 based on flexion-extension radiographs. Of these, only 78 were found to have a corresponding spondylolisthesis on MRI, leaving 31/109 (28%) of DS levels undiagnosed on MRI. No additional anterolisthesis cases were detected on standing flexion-extension verses standing lateral radiographs.ConclusionsRoutine standing lateral radiographs should be standard practice to identify DS, as nearly 1/3 of cases will be missed on supine MRI. This may have implications on whether or not an arthrodesis is performed on those patients requiring lumbar decompression. Flexion-extension radiographs demonstrated no added value compared with standing lateral x-rays for the purposes of diagnosing DS.

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